This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-227246 filed on Jul. 27, 2000.
1. Field of the Invention
The present invention relates to high density energy beam machining method and apparatus for the same in which high density energy beam is emitted to perform cut-machining.
2. Description of Related Art
Conventionally, when a work piece is cur-machined for removing unnecessary parts, forming a hole, and forming a thin groove, a high density energy beam machining method is used. In this method, a high density energy beam is emitted to a portion of the work piece, which is to be cut (cut-machined portion), for fusing and cutting the cut-machined portion. Generally, while this cut-machining is performed, assist gas such as nitrogen and oxygen is injected simultaneously with the emission of the high density energy beam for quickly removing dross and vaporized substance generated by the cut machining. In this way, the dross and vaporized substance are prevented from sticking to the work piece and a condensing lens of a work nozzle.
When the work piece is, as described above, cut-machined by blowing the assist gas from emission side of the high density energy beam, the dross D mostly flows to the lower side of the cut-machined portion due to the assist gas, and sticks to the periphery area of the cut-machined portion.
For preventing the dross from sticking, it is considered that assist gas is supplied from both the emission side of the high density energy beam and the opposite side thereof. Here, the assist gas supplied from one of them flows toward an opposite side through cut portion formed by the emission of the high density energy beam, and the assist gas supplied from the other of them flows along an inside or outside surface of the work piece.
According to the structure, when one of the assist gases flows through the cut portion and to the opposite side, the dross generated during the cut-machining is drifted and swept to the opposite side of the work piece through the cut portion. At the opposite side to which the dross is drifted and swept, the other assist gas flows along the inside or outside surface of the work piece, so that the dross drifted and swept to the opposite side is blown by the other assist gas. Thus, the dross is effectively prevented from sticking.
However, when the above described method is used for forming holes on a work piece having a hollow space thereinside, for example, when it is used for forming through holes on a cylindrical side wall of a cylindrical work piece, as shown in FIG. 9, a gas discharging nozzle 101 is disposed at one end of the cylindrical work piece 102. The high density energy beam HB is emitted from a work nozzle 103 to form a hole 104 on the work piece 102, and the assist gas supplied from the gas discharging nozzle 101 into the work piece 102 flows out to the outside through the hole 104. In this case, there arise following disadvantages.
Since the assist gas supplied from the gas discharging nozzle 101 into the work piece 102 flows out to the outside through the hole 104, the dross does not stick to an inner surface of the work piece. However, when the hole 104 is formed, the high density energy beam HB passes through the hole 104 and is emitted to the opposite side inner surface of the work piece, so that the emitted inner surface might be partially burned and melt.
When a large number of holes are formed, pressure and amount of the assist gas flowing out from the hole 4 is decreased, so that the pressure drifting and sweeping the dross is decreased. As a result, the dross tends to stick around holes being formed later.
A first object of the present invention is to prevent the high density energy beam passing through a cut portion formed by the energy beam from being emitted to an opposite side inner surface of a work piece.
A second object of the present invention is to prevent dross from sticking to the peripheral area of the cut portion.
According to the present invention, a discharging nozzle is provided in an inside space for supplying an assist gas from an inside of the work piece. The gas discharging nozzle shuts the high density energy beam intruding into the inside space of the work piece through the cut portion, so that the energy beam is prevented from being emitted to an opposite side inner surface of the work piece. The dross formed during the cut-machining is drifted and swept to the outside by an assist gas flowing out from the inside space of the work piece through the cut portion, and is blown out by the assist gas flowing on an outside surface of the work piece around the cut portion, thereby preventing the dross from sticking to peripheral area of the cut portion.